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Problems with nutrient flowing

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Fernando Aguilar, modified 3 Years ago.

Problems with nutrient flowing

Youngling Posts: 22 Join Date: 2/7/13 Recent Posts
Dear all,

We are running ECO model coupled to Delft3D to simulate water quality in a reservoir from April to October. The hydrodynamic model (Z-Model, 35 layers, 5 tributaries configured as discharges and 2 outflows, time step is 5 minutes) show no continuity problems and the water level follows fairly well the real data.

But when running the ECOWAQ model, the top layers are always visible, showing substances values, although these layers become dry in the FLOW model. Also we can appreciate that a continuous and very high load of nutrients (substances concentrations 6 magnitude orders over the real ones) is entering the lake during all the simulation time, aparently coming from these (4) top layers and their boundary cells in these, saturating with nutrienst all the simulation domain.
Christophe Thiange, modified 3 Years ago.

RE: Problems with nutrient flowing

Jedi Knight Posts: 125 Join Date: 11/15/12 Recent Posts
Hi Fernando,

Is the emersion process active?
FA
Fernando Aguilar, modified 3 Years ago.

RE: Problems with nutrient flowing

Youngling Posts: 22 Join Date: 2/7/13 Recent Posts
Yes, it is activated.
Christophe Thiange, modified 3 Years ago.

RE: Problems with nutrient flowing

Jedi Knight Posts: 125 Join Date: 11/15/12 Recent Posts
Hi Fernando,

If the water level drops relatively quickly, it could be that mass remains trapped in inactive surface layers. The high concentrations you see could be due to the small segment volumes in the surface layer. Transport from the upper layer can still occur with dispersion.

Hard to guess what is going on without more details. Uploading your model or at least the inp and lst files may help.

In any case, some workarounds you can try:
  • Use the no dispersion if flow rate is zero option (to avoid dispersion from the upper layer)
  • Aggregate the top layers vertically, so that the top layer never runs dry (drawback is that you will loose resolution near the surface, obviously)